Although insertion of needles into the human vascular network is commonly considered by medical professionals to be one of the most routine and easily performed activities, such a "simple" technique is traumatic, painful and dangerous for the patient. Erroneous attempts to penetrate the arterial-venous system are not rare in medical practice, causing numerous injuries to the patient.
Penetration of the vascular network is necessary for two main reasons: extraction of blood for laboratory analysis or delivery of fluids and/or different agents of contrast used in angiographic techniques. The consequences due to missed puncture of the vein include the need for repeated puncture causing the patient to feel further threatened, discomfort, pain, sweat, fear, and in difficult patients loss of cooperation while performing the puncture. Extravasation of agents of contrast due to a missed vein puncture can cause terrible pain, sweat and necrosis of the place of puncture in some cases.
Certain patient groups are known to be more difficult to properly puncture. The classical groups include: overweight people, young women, infants (especially premature babies) and young children, dark-skinned people and people in shock.
Apparatus for visualization of the subcutaneous vessels are known, and an example of current imaging technology is disclosed in U.S. Pat. No. 4,817,612 to Pennypacker et al, in which a two-dimensional vein location system is described. Working under a two-dimensional image causes more damage than working without an imager. Because there is no depth sensation, the access of the needle in relation to the arm will be incorrect, necessitating repetitive puncturing.
U.S. Pat. No. 5,519,208 to Esparza et al discloses a two-dimensional vein location system which requires the attachment of an LED to the tip of the needle. A light of this sort will be emitted tangentially, causing bad scattering of light on the area of inspection in relation to the optical axis of the human eye. If the infrared light comes from the wrong direction the light will not be able to provide the proper information. Infrared light which is applied to the human body must be scattered uniformly to distinguish the fine details of the veins before any electronic manipulation of the image has been done. Improper illumination cannot be corrected with the use of an image processor, since information which does not exist on the image because it has not been properly illuminated cannot be enhanced by any image processor. In addition the attachment of an LED to the tip of the needle necessitates providing a power source to feed the LED. Currently, disposable needles are used almost exclusively, making this design impractical.
U.S. Pat. No. 5,608,210 to Esparza et al mentions the visual sensation of three dimensions, although the apparatus described therein is unwieldy, and is designed to be worn on the head. This demands that the health care providers change their style of working. Although this method has been used in the indirect ophthalmoscope for more than 50 years, the modern instrument reaches a weight of only 300-350 grams. Attempts by many companies to introduce a more sophisticated head-worn opthalmoscope with a video system have resulted in failures due to the weight and the instability of the image due to head movement. These obstacles apply to a head-worn vascular imager as well. Other attempts at head-worn imagers include a military infrared viewer mounted on the head or worn on goggles. This device was rejected because the weight did not allow maintenance of a constant image in accordance with the optical axis of the eye.
Although the Esparza '210 patent does provide a certain three-dimensional sensation, the effect is actually more theoretical than practical as the distance from the eyes of the user to the subject must be fixed, otherwise the cameras need to be refocussed, so that both cameras are tilted to a convergent point on the subject. If the distance from the eyes of the user to the subject is reduced the convergent point is crossed and the three-dimensional effect is lost. In order to hold a video screen (or two) in front of the user's eyes, optical lenses are required with a refractive power which is determined so as to correct the shorter distance accepted by the human eye. This would cause discomfort to the user upon removal of the apparatus until the eyes would readjust to their normal focus. This discomfort could include dizziness, nausea and headaches.
Therefore, it would be desirable to provide an imager with proper illumination which would provide a clear three-dimensional image in real time so as to improve the success rate of health care providers in penetrating the vascular system. This would allow the patient to both feel at ease and comfortable, thereby lowering the stress level of patients who fear an inaccurate puncture and also lowering the incidence of medical complications resulting from an inaccurate puncture.